1. Field of the Invention
The present invention relates to a hydraulic damping device for vehicles. It is particularly suitable for an insertion between two rigid structures, such as a vehicle chassis and an engine as an engine mounting, for the purposes of damping and supporting such structures.
2. Description of Related Art
A conventional hydraulic damping device for a vehicle is shown in FIG. 1.
A similar conventional device is disclosed in the U.S. Pat. No. 4,607,828.
As shown in FIG. 1, a hydraulic damping device 10 has a main damping body 1, a flexible membrane 2, a main liquid chamber A, an auxiliary liquid chamber B, a partition 3, a passage 4, a metal side wall 5, on upper-side supporting member 7 and a lower-side supporting member 6.
The main damping body 1 is formed with a frustoconic shape from a thick rubber wall, and defines an interior liquid chamber extending across the bottom half of the device. The upper-side supporting member 7 is provided with a bolt 8, which is connected to one of the rigid structures, such as engine not shown. Also, the main damping body 1 is connected to the tubular metal side wall 5, at lower and outer peripheral portions thereof by vulcanization. The upper-side supporting member 7 is also fixed to the main damping body 1 by vulcanization.
The flexible membrane 2 is made of a thin rubber sheet, such as bellows or diaphragm, and closes a lower opening of the main damping body 1 for providing the liquid chamber between them.
The partition 3 is provided in the liquid chamber and divides the liquid chamber into a main liquid chamber A and an auxiliary liquid chamber B. Also, the partition 3 has an annular passage 4 which is formed about an outer peripheral portion and cooperates with an inner surface of the main damping body 1.
The passage 4 has two holes 11, 12 which open into the main liquid chamber A and the auxiliary liquid chamber B, respectively. Therefore, the main liquid chamber A leads to the auxiliary liquid chamber B through the passage 4.
The metal side wall 5 has an annular U-shaped portion 15 at a lower portion. This portion provides a connection for the metal side wall 5 to the lower-side supporting member 6, partition 3 and the flexible membrane 2 at the annular U-shaped portion 15 by clamping.
The lower-side supporting member 6, which is formed to a dish shape, has a bolt 13 at the center portion for connecting to the other of rigid structures, such as vehicle chassis not shown.
The hydraulic damping device 10 is assembled by clamping elements together at the annular U-shape portion 15, and the device 10 has two deformable chambers filled with a damping liquid, separated by the partition 3.
When the device 10 is vibrated during vehicle use, the main damping body 1 is deformed. As such deformation occurs, the filled damping liquid flows from the main liquid chamber A to the auxiliary liquid chamber B through the passage 4 and the respective openings 11 and 12. Vibration is absorbed by the deformation of the main damping body 1 and the flowing of the filled damping liquid through the throttled passage 4.
However, in above conventional device 10, the passage 4 is formed from one plate, such a partition 3, to make the U-shaped outer peripheral portion in the cross-section. Formation of the passage 4 is not easy to achieve on partition 3. For that reason, various devices have been proposed to make formation of the passage 4 on the partition 3, more easily accomplished, for example, Japanese Patent Laid-open publication No. Sho 61-197833 and Japanese Patent Laid-open publication No. Sho 62-127536. These references disclose different modifications of a partition wall to improve forming. For example, the partition is constructed from two plate members which overlap to form the passage, or the passage is made from one plate by drawing or squeezing the plate.
The two piece partition necessarily increases the number of parts and requires many additional manufacturing steps. Where plates are drawn formation of the partition requires complicated shapes, and involves many additional manufacturing steps, more time and additional cost.
Further, the above conventional hydraulic damping device 10 has a large diameter to produce the desired sealing between both liquid chambers A, B and the outside of the liquid chamber at the clamping portion where the annular U-shaped portion 15 of side wall 5 is connected to membrane 2, partition 3 and the supporting member 6. This large diameter makes the device 10 bigger so that extra space is taken up in an otherwise small engine compartment.